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Geosystems - Water
Flashcards for my Geosystems course.
| Question | Answer |
|---|---|
| What are the two paths of water once it’s reached the earth's surface? | Runoff and groundwater addition through infiltration and percolation. |
| What is an aquifer? | A permeable body of rock that can contain or transmit a usable amount of water. |
| What is the water table? | The layer below the unsaturated zone and above the saturated zone, part of ground water. It creates springs or feed lakes or riverbeds where it intersects surface. |
| Contrast influent and effluent conditions. | Influent conditions occur in arid zones, when water in streams lies higher than the water table, causing them to dry out seasonally. Effluent conditions have a high water table that contributes to stream flow. |
| When does a cone of depression occur? | When something drawing water to the surface from the water table, such as a well, overdraws the capacity of the water table. This causes drawdown, which makes an area of the water table depressed in a cone shape. |
| What are the three types of uses for runoff? | Instream uses like ecosystem preservation, waste water dilution, hydroelectric, fishing resources. Withdrawn uses like industry, agriculture. Consumptive uses like evaporated water in steam-electric plants. |
| What two forces drive fluvial systems and the hydrological system? | Insolation and gravity. |
| What is the base level of a stream? | The level below which a stream cannot erode its valley further. The ultimate base level is sea level but there are also local base levels that vary widely. |
| What is a drainage basin? | An area surrounded by ridges that gives all its runoff into a stream. The catchment area of the drainage basin is the watershed of the stream. Large, continental drainage basins are divided into many smaller ones. |
| What is a floodplain? | A flat, low-lying area around a stream channel that is subject to recurrent flooding. Natural levees form around it, called stream terraces, which can be stepped. |
| How do deltas form? | Velocity suddenly decreases when a stream enters a larger body of water, causing it to drop all of its sediment. |
| What is groundwater? | Beneath the surface but tied to surface supplies. Largest potential source of freshwater (22%). Water table collects at base of saturation zone. |
| How does water become part of groundwater? | Surplus water percolates through ground b/c of gravity, through aerated (unsaturated) zone to the saturated zone. |
| Describe the longitudinal profile. | River begins steep at headwaters, evens out as it nears delta. Water goes from turbulent flow, high energy, with gravel sediment, to laminar flow with clay and silt – in between, coarse sand and sand bits. |
| Describe erosion/deposition patterns in different parts of the longitudinal profile. | There is high erosion at the beginning and high deposition at the end because the water moves faster and can carry sediment better than slow water. |
| What ways can the longitudinal profile of a river change (human‐caused, other causes)? | Sea levels rise in association with global warming, dams, flooding, channelization |
| How is stream discharge measured? | Discharge(Q)=wdv Should measure depth at several points across |
| How does stream discharge change downstream? | Downstream, discharge has more space to move, it moves slower and is more shallow. |
| What can affect stream discharge? | Flooding increases discharge, drought decreases it. Gradient and velocity also affect what discharge does to stream bed in terms of erosion and carrying power. |
| Describe the process of erosion. | Hydraulic action loosens and lifts rocks and they are carried along stream, causing abrasion. Velocity and volume important determinants. |
| How do you measure stream velocity? | Multiply surface speed by .8 |
| What are the five main stream characteristics? | Discharge, erosion, deposition, transport, channel characteristics (depth, width, velocity, types of sediment, etc) |
| What’s a nickpoint? | An abrupt change in stream gradient, like a waterfall or rapids. Conversion from potential to kinetic energy is concentrated as water tries to erode nickpoint. Can happen when stream erodes to level of resistant rock. Migrate upstream. |
| What are the three types of stream transport? | Stream transport is a function of velocity. Dissolved (ex. Salt), suspended (fine grains), bedload (larger bits clunked along riverbed) |
| What forms a braided stream? | Streamload exceeds capacity, causes aggradation, stream channels builds up. Stream flows in interconnected maze over deposition. Reduced discharge or landslide upstream, glacial meltwater might cause this. |
| What causes a meandering stream? | Gradual slopes, stream becomes snake-like. Outer curve eroded, inner curve lotsa deposition. |
| What forms an oxbow lake? | When a meander erodes and deposits until the meander is almost touching the next one, it sometimes erodes through and connects the two meanders, leaving one out, which is disconnected from stream. |
| What is the zone of aeration? | The unsaturated zone above the capillary fringe, where water can percolate downward through gravity. |
| What is the capillary fringe? | Area below zone of aeration that moves water from zone of saturation upwards through capillary action. |
| What is the zone of saturation? | Zone below the zone of aeration and capillary fringe that has all of its air replaced by water. |
| What is an aquiclude? | A body of rock that does not conduct water in usable amounts. |
| Describe a confined vs unconfined aquifer. | Zone of saturation is an unconfined aquifer, a water-bearing layer that is not confined by an overlaying/underlaying impermeable layer, which would be a confined aquifer. |
| What is a potentiometric surface? | Water in a confined aquifer, under pressure under its own weight, creating pressure level. If allowed to equalize, it would be at the pontentiometric surface. |
| What is saltwater intrusion? | When aquifers are overpumped near saltwater, it can migrate inland and the groundwater becomes brackish, useless as a freshwater source. |
| Describe discharge and recharge of groundwater. | Groundwater is recharged where water has time to infiltrate – steep slopes are not recharge zones but flat, sparsely vegetated areas are. Discharge is from vegetation, effluent streams. |
| What are some human effects on groundwater? | Landfill seepage, wells, septic tanks, industrial seepage can cause lowered water table, artesian wells (potentiometric surfaces), seawater intrusion, cones of depressions, dried surface sources. |
| Describe hydrologic cycle in the Puget Sound Basin. | 9.5% airborne water from Pacific stays in W. WA, the rest goes over E. WA. Orographic lifting by Cascades and Olympics causes snow and the watershed. Glacial land makes surface water almost as plentiful. Effluent conditions. Lotsa vegetation. |
| Describe Puget Sound freshwater/seawater interactions. | Tides and currents in Sound affected by islands and small channels. Tides act like a pump and move dense saltwater with more buoyant freshwater throughout estuary. Mixes on average 2times/yr. |
| Describe the major Puget Sound sills. | Four major basins separated by sills (Admiralty Bay separates Strait of Juan de Fuca and Puget Sound, Hood Canal, Tacoma Narrows). |
| Describe length and average depth of Puget Sound. | 100 miles long from Deception Pass to Olympia. 450 ft average depth, 930 ft max. |
| What are the major river basins in the Puget Sound watershed? | Samish, Nooksack, Skagit, Stillaguamish, Snohomish, Lake Washington Drainage, Green River, Puyallup, Nisqually, Dechutes, Puget Sound, Skokomish, Hood Canal, Elwha and Dungeness Rivers |
| Describe the history of Duwamish region rivers, including Duwamish, Black, Cedar, White, Puyallup Rivers, Lake Washington. | Orig. White & Green formed Black to create Duwamish. 1906 White flooded & changed course to Puyallup. 1911, Cedar rerouted to flow into L. WA instead of Black. Ship canal dug 1916, lake dropped 9 ft & flowed to Sound instead; Black dried up. |
| Describe briefly the geography of the Green River. | Watershed is 492 square miles, river is 65 miles from Elliott Bay to Howard Hanson Dam. It flows from the Cascade range into the Duwamish and ends at Harbor Island. |
| What is the average discharge of the Green River? | Average discharge 1300 cubic ft/sec. |
| What are the Green River tributaries? | Enumclaw creek, Mill Creek, Big Soos Creek |
| Pre-human settlement history. | Glaciers came down from Canada, quickly receded. 13,000 ya Puget Sound was a huge bay. 5,000 ya Osceola mudflow when Mt Rainier erupted, filled in rivers and created modern Puget Sound formation. |
| Post-human settlement history. | 1906, White diverted to Puyallup for flood control, reduced 30%. Black and Cedar flow toward L. WA, reduced 40% of orig. Estuary tidelands filled, drained, dredged. Channelized & diked for flood & and navigation. 1962, Howard Hanson Dam. |
| Describe Green Riverwater quality. | The Duwamish Waterway is a superfund site. Green River Watershed is protected land and is considered quite clean - it’s Tacoma’s municipal water supply. |
| Dam threats: to water quality, quantity, water‐related ecosystems. | Floods huge area, creates more surface area for evap. Methane emission de rotting plants. Sediment deposition, none left after dam. Erosion along stream and coast, no sediment to replace wave erosion. Temp increase in winter and decrease in summer. |
| Describe the Howard Hanson dam history. | Built 1962 just after a devastating flood. Floods had been annual. Successful in stopping them. |
| Howard Hanson affects on Green River, current issues: | Forms water reservoir for Tacoma. City has to release more water than usual this year, Auburn is susceptible to floods. |
| Green River: Effective cleanup approaches, current efforts, effective organizations. | Annual Green River clean up (24 yrs). Middle Green River Coalition kept Tacoma from diverting all water. |
| Describe the percentages of saltwater, freshwater, ice, groundwater, surface water. | Saltwater (97.5%), Freshwater (2.5% - 68.9% of that is ice, .3% lakes and rivers, 30.8% in ground). |
| Describe surface water and groundwater availabilities by continent. | N.A. (some ice, 3 gr w, 3 sur w), S.A. (4 gr w, 4 sur w), Af. (2 gr w, 1 sur w), Asia (some ice, 1 gr w, 2 sur w), Eur. (less ice, 5 gr w, 5 sur w), Aust. (6 gr w, 6 sur w) Ant. (lotsa ice), Greenland (lotsa ice) |
| What role does evaporation play in surface water use? | Most freshwater is stored in reservoirs for electricity generation. In hot climates, there’s a lot of water lost to evaporation. |
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